Isoamylase (Glycogen 6-glucanohydrolase)

The fractionation and reconstitution method was employed to investigate the impact of different proportions of A-type (AS) and B-type (BS) wheat starch on the quality of liangpi and its potential mechanism, with traditional gluten-removed liangpi (RGL) as a control. The results demonstrated that a higher AS/BS ratio led to an increase in hardness, resilience, and chewiness. Moreover, the sensory scores for BS-dominated liangpi were significantly lower than those for AS-dominated liangpi, and liangpi with 60 % AS had the highest sensory scores. Additionally, as the AS/BS ratio increased, the G′ and G″ values of the samples gradually rose, while the tan δ value exhibited a corresponding decrease. The morphological results showed that with the increase of AS/BS ratio, the microstructure of liangpi had larger but fewer pores. Furthermore, the XRD and FTIR analyses demonstrated an increase in ordered structures among starch granules with higher ratios of AS/BS, resulting in stronger hydrogen bonds in the AS-dominated liangpi. This study provides a comprehensive understanding of how the proportion of AS and BS influences the quality of liangpi, offering valuable insights for enhancing the quality of liangpi by adjusting the AS/BS ratio during the production process.

Rice with high resistant starch (RS) exhibits the potential to improve glucose metabolism, insulin sensitivity. In this study, using two rice varieties—Samgwang, a medium-amylose rice, and Dodamssal, a high-amylose rice containing RS—we analyzed the composition and molecular structural characteristics of brown rice and its starch and the effects on fasting blood glucose levels, fecal short-chain fatty acid (SCFA), and gut microbiota after 8 weeks of consumption in mice. The amylose content of heat-treated Samgwang (HS) and -Dodamssal (HD) was 21.0 ± 0.2 and 47.5 ± 0.3 %, respectively, while RS contents were 0.8 ± 0.0 and 14.7 ± 1.0 %. HD exhibited a C-type starch crystallinity with a lower proportion of short chains and a higher proportion of long chains compared to HS. HD-fed mice exhibited lower fasting blood glucose levels and the highest SCFA levels in their feces. They also had the highest abundance of Ruminococcus bromii, an RS-degrading bacterium, the highest positive correlation with Faecalicatena fissicatena (r = 0.9), and the highest negative correlation with Lachnoclostridium scindens and Lawsonibacter asaccharolyticus (r = −0.8). Overall, HD consumption can improve glucose metabolism by increasing intestinal SCFA production and can serve as a prebiotic dietary ingredient to improve obesity and diabetes.

The molecular and supramolecular structures of japonica and waxy rice starches under high hydrostatic pressure treatment (450 MPa) were studied and the changes in physicochemical properties were analyzed based on these structures. The molecular structures of japonica and waxy rice starch cause differences in the lamellar structure and physicochemical properties. The thickness of amorphous lamella of japonica rice starch increased at 5 min (2.95 nm) followed by a gradual collapse of lamellar structure. Whereas the thickness of crystalline lamellae of waxy rice starch increased at 15 min (5.92 nm) and the lamellae collapsed suddenly at 20 min. The pasting, rheological and textural characteristics of both starches increased significantly within 10 to 15 min. The decreasing onset temperature and enthalpy of high hydrostatic pressure-treated starches indicated easier gelatinization. High hydrostatic pressure-treatment offers potential for developing starch-based products with low swelling capacity, easy gelatinization, high viscosity and hardness.

Red microalgae from the Cyanidiophyceae, particularly Galdieria sulphuraria and Cyanidioschyzon merolae, are primitive photosynthetic thermoacidophiles that thrive in acidic hot springs and geysers. Unlike most Cyanidiophyceae, Galdieria strains are metabolically flexible as they can switch from photoautotrophic growth in the light to heterotrophic growth in complete darkness. Galdieria sulphuraria is especially noteworthy for its accumulation of various commercially valuable, functional compounds such as glycogen and phycocyanin. Glycogen, a branched fractal-like polysaccharide composed of several thousands of anhydroglucopyranose units, can be added to cosmetic products and sports drinks as a moisturizer or slow-digestible carbohydrate. While the production and structural characteristics of the glycogen of G. sulphuraria 108.79, isolated from Yellowstone National Park, have been previously described, our investigation aimed to explore glycogen production and properties across various Galdieria strains from different locations. Our findings reveal that all examined strains produce substantial amounts of highly branched glycogen when grown heterotrophically on glycerol in the dark. Notably, the structural characteristics of Galdieria glycogen distinguish it from both eukaryotic and prokaryotic glycogen, exhibiting a significantly higher degree of branching, substantially shorter side chains, and a considerable extent of indigestibility. These findings support the hypothesis that this highly branched, small glycogen is a long-term energy store, enabling survival during extended periods of complete darkness.

To investigate the potential of inhibiting starch retrogradation by modifying the functional groups of starch, transglucosidase (TG) was used to facilitate active hydroxyl groups to be exposed through increasing branching degree. Subsequently, hexose oxidase (HOX) advantageously promoted the oxidation of starch chains and increased spatial repulsion of starch backbone. The Fukui Function revealed that the oxygen atoms at the C3 and C4 positions on glucose units had a higher oxidation tendency. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis confirmed that the reactive hydroxyl groups underwent an oxidation process with increasing HOX treatment time. From the crystal structure parameters, the c-axis of native corn starch modified by TG for 16 h and HOX for 48 h (or TGHOX-48) was shortened from 16.92 to 16.32 Å and in the long-term retrogradation, TGHOX-48 exhibited the lowest starch retrogradation rate (0.22).

The detailed relationships among starch fine molecular structures, gut microbiota, and short-chain fatty acids (SCFAs) are not fully understood. We hypothesized that specific starch molecular size and chain-length distribution are favored by gut bacteria for the secretion of SCFAs. To investigate this, different types of starches with diverse molecular size and chain-length distributions (e.g., amylose content ranging from about 1 % to 38 %) were subjected to in vitro fermentation with human fecal inocula. Tapioca and waxy maize starches were notably more effective at producing acetate and propionate compared to lentil, wheat, and pea starches (p < 0.05). Correlation analysis revealed, for the first time, that the number of amylose chains with a degree of polymerization between 500 and 5000 was positively correlated with the abundance of Bacteroides_coprocola_DSM_17136 and Bacteroides_plebeius, possibly relating to the higher production of acetate and propionate. These results indicate that starches with certain fine molecular structures could be used to target gut bacteria to produce various types of SCFAs, thereby amplifying beneficial effects on human health.

To improve paste stability of cassava starch, including acid resistance, high-temperature shear resistance and freeze-thaw stability, cassava starch was modified by sequential maltogenic amylase and transglucosidase to form an optimally denser structure, or branched density (12.76 %), molecular density (15.17 g/mol/nm³), and the proportions of short-branched chains (41.41 % of A chains and 44.01 % of B1 chains). Viscosity stability (88.52 %) of modified starch was higher than that (64.92 %) of native starch. After acidic treatment for 1 h, the viscosity of modified starch and native starch decreased by 56.53 % and 65.70 %, respectively. Compared to native starch, modified starch had lower water loss in freeze-thaw cycles and less viscosity reduction during high-temperature and high-shear processing. So, the appropriate molecular density and denser molecule structure enhanced paste stabilities of modified starch. The outcome expands the food and non-food applications of cassava starch.

In this paper, a range of novel cluster dextrins (CDs) with high molecular weight (~10⁵ g/mol) and narrow molecular weight distribution were fabricated by α-amylase and branching enzyme (BE, EC 2.4.1.18). The influence of CDs on the physicochemical properties of κ-carrageenan (KC) emulsion gels was investigated. The average particle size of the composite emulsion gels containing CD was decreased by 7.85–12.66 μm, and the gel network was more uniform and denser, owing to stronger non-covalent interactions in the composite sample system. Textural results demonstrated that the composite emulsion gels exhibited higher hardness and springiness, but lower cohesiveness. CDs hindered the formation and aggregation of KC double helices, as evidenced by reducing the intensity of the sulfate group peak at 1223 cm⁻¹. Furthermore, CDs increased the apparent viscosity, storage modulus (G'), and melting temperature (T_m) of emulsion gels, based on rheological results. CDs with longer branch lengths were more prone to entangle with KC chains to optimize the gel structure, exhibiting a more significant effect on the physicochemical properties of emulsion gels. The present study provided a new insight for constructing a new energy delivery system.

This study aims to explore the formation mechanism of starch structure and the relationships between the appearance quality and starch structure of soft rice under different nitrogen levels. We comprehensively investigated the physiological aspects, starch structure variations, and appearance quality of soft rice in response to different nitrogen applications. The results showed that under the moderate nitrogen application (270 N), the soft rice exhibited the highest AGPase activity, the highest large-starch granule content, and the lowest chalkiness. Under the highest nitrogen application (360 N), the soft rice exhibited the highest GBSS and DBE activity and the lowest SBE activity, the highest content of long-branched amylopectin, the lowest relative crystallinity, the fewest ordered structures, the most amorphous structures, the largest semi-crystalline lamellar thicknesses, and the highest transparency of chalk-free rice. In conclusion, moderate nitrogen fertilization (270 N) improved the AGPase activity, which leaded to fuller starch granules and more compact endosperm in soft rice. Thus, the grain chalkiness of soft rice decreased. Continuous nitrogen application (0-360 N) constantly increased the GBSS and DBE activity and reduced the SBE activity in soft rice, leading a lower content of short-branched amylopectin and a higher content of long-branched amylopectin in soft rice. Thus, the relative crystallinity and ordered structures of soft rice were reduced. These structures improved the transparency phenotype of soft rice.

High V-type relative crystallinity (V_RC) dextrin (HVD) was prepared by high-temperature acid-ethanol hydrolysis (HTAEH) of V-type granular starch (VGS). The influence factors including acid concentration, acidolysis temperature and acidolysis duration on HVD production were investigated along with the formation mechanism. HVD with the highest V_RC (45.15%) was prepared in 60% (v/v) ethanol at an HCl concentration of 2.0% (w/w), an acidolysis temperature of 95°C and an acidolysis duration of 30 min. Increasing V_RC during the first stage of HTAEH indicated that the V-type crystalline region of VGS was resistant to acid hydrolysis. The molecular weight of VGS was significantly decreased after 10 min ~30 min of HTAEH but remained relatively constant thereafter. The increase in V_RC of HVD was due to acid hydrolysis of amylose (AM), and degraded AM with a peak degree of polymerisation of 107 was more easily to complex with ethanol.